The capability to produce high-quality graphene on a large scale has become a key factor in commercializing graphene-based technologies. Graphene exhibits extraordinary properties which can be utilized for many applications in various fields of science and engineering. A reliable, fast and economical fabrication technique is necessary for the commercialization of graphene-based products. Current techniques for producing graphene devices involve the use of photolithography or e-beam lithography to produce graphene devices having the necessary structures. Some of the disadvantages of these processes include high processing cost, long processing time, low yield, and unwanted doping of graphene. In addition, these processes are not compatible with flexible polymer substrates. Techniques where graphene patterns are printed using graphene ink overcome these disadvantages, but do not provide a continuous printed pattern. Hence, such techniques have limited use in applications such as nanoelectronics where the continuity of the graphene pattern may be critical to the performance of the device. Further, a continuous monolayer of graphene ribbon exhibits higher values of carrier mobility than a similar pattern printed with graphene ink.
The placement of electronic devices on flexible substrates has been a growing area for research and development due to rapidly expanding applications and markets for touch screens, electronic paper and displays, photovoltaics, lighting, and sensor tags. To achieve the economy of scale for large-area substrates requiring active transistor functionality, the primary focus has been to fabricate the electronics directly on the flexible substrate. The most promising materials and processes to date include thin-film metal oxide materials deposited by moderate temperature processes such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), yet there are still concerns associated with substrate compatibility, throughput, and subsequent process integration for final device and circuit designs.
Conventional transparent conducting electrodes make use of indium tin oxide (ITO) and are commonly used in solar cells, touch sensors and flat panel displays. ITO is an essential element in virtually all flat-panel displays, including touch screens on smart phones and iPads, and is an element of organic light-emitting diodes (OLEDs) and solar cells. The element indium is becoming increasingly rare and expensive. ITO is also brittle, which heightens the risk of a screen cracking when a smart phone is dropped, and further rules ITO out as the basis for flexible displays. Graphene film is a strong candidate to replace ITO due to its high conductivity, good transparency, and good mechanical flexibility. Efforts to make transparent conducting films from large-area graphene, however, have been hampered by the lack of efficient methods for the synthesis, patterning and transfer of graphene at the scale and quality required for applications in high performance nanoelectronics.
Two properties of graphene (i.e., electron mobility and material flexibility) may be employed to facilitate the development of electronic components and circuits for various applications, such as flexible screens and very-high-performance transistors and electronic components. Recently, the large-scale growth of high-quality graphene on metal using CVD has enabled various applications. The fabrication of the graphene-based active component, however, requires complex, expensive and time-consuming processes using conventional lithography techniques. A simple process for the production of both graphene patterning and graphene transfer patterns is urgently needed to enable the fabrication of marketable graphene devices.